arXiv subjects

S. Kelley

Publications and source records attributed to S. Kelley.

12 recordsLinked to original sources

arXiv2026

Cedalion Tutorial: A Python-based framework for comprehensive analysis of multimodal fNIRS & DOT from the lab to the everyday world

Functional near-infrared spectroscopy (fNIRS) and diffuse optical tomography (DOT) are rapidly evolving toward wearable, multimodal, and data-driven, AI-supported neuroimaging in the everyday world. However, current analytical tools are fragmented across platforms, limiting reproducibility, interoperability, and integration with modern machine learning (ML) workflows. Cedalion is a Python-based open-source framework designed to unify advanced model-based and data-driven analysis of multimodal fNIRS and DOT data within a reproducible, extensible, and community-driven environment. Cedalion integrates forward modelling, photogrammetric optode co-registration, signal processing, GLM Analysis, DOT image reconstruction, and ML-based data-driven methods within a single standardized architecture based on the Python ecosystem. It adheres to SNIRF and BIDS standards, supports cloud-executable Jupyter notebooks, and provides containerized workflows for scalable, fully reproducible analysis pipelines that can be provided alongside original research publications. Cedalion connects established optical-neuroimaging pipelines with ML frameworks such as scikit-learn and PyTorch, enabling seamless multimodal fusion with EEG, MEG, and physiological data. It implements validated algorithms for signal-quality assessment, motion correction, GLM modelling, and DOT reconstruction, complemented by modules for simulation, data augmentation, and multimodal physiology analysis. Automated documentation links each method to its source publication, and continuous-integration testing ensures robustness. This tutorial paper provides seven fully executable notebooks that demonstrate core features. Cedalion offers an open, transparent, and community extensible foundation that supports reproducible, scalable, cloud- and ML-ready fNIRS/DOT workflows for laboratory-based and real-world neuroimaging.

eess.SP↗

arXiv2023

NiSi: New venue for antiferromagnetic spintronics

Envisaging antiferromagnetic spintronics pivots on two key criteria of high transition temperature and tuning of underlying magnetic order using straightforward application of magnetic field or electric current. Here, we show that NiSi metal can provide suitable new platform in this quest. First, our study unveils high temperature antiferromagnetism in single crystal NiSi with $T_{N} \geq 700$ K. Antiferromagnetic order in NiSi is accompanied by the non-centrosymmetric magnetic character with small ferromagnetic component in a-c plane. Second, we find that NiSi manifests distinct magnetic and electronic hysteresis responses to field applications due to the disparity in two moment directions. While magnetic hysteresis is characterized by one-step switching between ferromagnetic states of uncompensated moment, electronic behavior is ascribed to metamagnetic switching phenomena between non-collinear spin configurations. Importantly, the switching behaviors persist to high temperature. The properties underscore the importance of NiSi in the pursuit of antiferromagnetic spintronics.

cond-mat.mtrl-sci↗

arXiv1995

Dynamical Determination of the Fundamental Couplings

We demonstrate that supergravity models containing the Standard Model, dilaton and modulus naturally lead to dynamical symmetry breaking with excellent phenomenology. We assume primordial supersymmetry breaking in the form of a constant contribution to the superpotential. String inspired relations link fundamental couplings to the dilaton vev. We specialize to a class of models inspired by the $4$-$D$ fermionic string. Non-renormalizable terms in the superpotential naturally produce the Higgs mixing parameter $μ$ suitable for our mechanism. We discuss extensions and limitations of our approach.

hep-ph↗

arXiv1995

Upper bounds on supersymmetry breaking from gauge coupling unification

I derive conservative upper bounds on the supersymmetry breaking parameter $m_{1/2}$ as a function of the strong coupling in the Standard Supersymmetric Model (SSM) using gauge coupling unification. I find that over more than $99\%$ of the parameter space, $α_3>0.120$ implies that $m_{1/2}$ is below $10\TeV$ and $α_3>0.129$ implies that $m_{1/2}$ is below $1\TeV$. I express the variation of these bounds over the SSM parameter space with a numerical coefficient, $c$. I also find that in the SSM, a reasonable value of $50\GeV 0.119$ over the whole parameter space. These bounds are particularly sensitive to the value of $\sin^2θ_W=0.2317\pm0.0005$ used in the calculation. In more realistic models, heavy thresholds and gravitational effects will modify this result. Although these effects are theoretically calculable in specific models, more realistic models contain many unknown parameters in practice. I illustrate this point with minimal supersymmetric $SU(5)$ where the combined constraints of gauge coupling unification and proton decay require $α_3>0.119$ for $m_{1/2}<1\TeV$ and the upper bound on the supersymmetry breaking scale is greatly relaxed.

hep-ph↗

arXiv1994

New phenomena in the standard no-scale supergravity model

We revisit the no-scale mechanism in the context of the simplest no-scale supergravity extension of the Standard Model. This model has the usual five-dimensional parameter space plus an additional parameter $ξ_{3/2}\equiv m_{3/2}/m_{1/2}$. We show how predictions of the model may be extracted over the whole parameter space. A necessary condition for the potential to be stable is ${\rm Str}{\cal M}^4>0$, which is satisfied if $\bf m_{3/2}\lsim2 m_{\tilde q}$. Order of magnitude calculations reveal a no-lose theorem guaranteeing interesting and potentially observable new phenomena in the neutral scalar sector of the theory which would constitute a ``smoking gun'' of the no-scale mechanism. This new phenomenology is model-independent and divides into three scenarios, depending on the ratio of the weak scale to the vev at the minimum of the no-scale direction. We also calculate the residual vacuum energy at the unification scale ($C_0\, m^4_{3/2}$), and find that in typical models one must require $C_0>10$. Such constraints should be important in the search for the correct string no-scale supergravity model. We also show how specific classes of string models fit within this framework.

hep-ph↗

arXiv1994

Using Gauge Coupling Unification and Proton Decay to Test Minimal Supersymmetric SU(5)

We derive a one-loop expression, including all thresholds, for the mass of the proton decay mediating color triplets, $M_{D^c}$, in minimal supersymmetric SU(5). The result for $M_{D^c}$ does not depend on other heavy thresholds or extra representations with SU(5) invariant masses which might be added to the minimal model. We numerically correct our result to two-loop accuracy. Choosing inputs to maximize $M_{D^c}$ and $τ_P$, within experimental limits on the inputs and a $1~TeV$ naturalness bound, we derive a strict bound $α_3>0.117$. We discuss how this bound will change as experimental limits improve. Measurements of $α_3$ from deep inelastic scattering and the charmonium spectrum are below the bound $α_3>0.117$ by more than $3σ$. We briefly review several ideas of how to resolve the discrepancy between these low values of $α_3$ and the determinations of $α_3$ from LEP event shapes.

hep-ph↗

arXiv1993

Testing Unified Supersymmetric Models

I define the Standard Supersymmetric Model (SSM) as the minimal supersymmetric extension ofthe Standard Model with gauge coupling unification and universal soft supersymmetry breaking at the unification scale. This well-defined model has a five-dimensional space of unknown parameters ($m_t, \tanβ, m_{1/2}, m_0, A$). I outline the top-down and bottom-up methods of solving this model. Thresholds may be treated either by dropping heavy particles from the RGE's or by considering loop corrections to the vacuum energy. Substantial regions of the parameter space are consistent with all experimental constraints. I consider the relation of the SSM to more realistic models such as supersymmetric $SU(5)$, Flipped $SU(5)\times U(1)$, the String-Inspired Standard Model, and string-derived models. I briefly discuss sparticle spectroscopy and flavor changing neutral currents (FCNC's) as sample methods for determining the unknown parameters of the SSM, and discriminating between the SSM and more realistic models.

hep-ph↗

arXiv1993

Exact Supersymmetric Amplitude for \kkb\/ and \bbb\/ Mixing

We present the most general supersymmetric amplitude for \kkb\/ and \bbb\/ mixing resulting from gluino box diagrams. We use this amplitude to place general constraints on the magnitude of flavor-changing squark mass mixings, and compare these constraints to theoretical predictions both in and beyond the Minimal Supersymmetric Standard Model.

hep-ph↗

arXiv1992

Evidence For SUSY from GUTS? Evidence For GUTS From SUSY!

We review the theoretical and experimental status of minimal grand unified theories (GUTS), contrasting the failure of minimal non-supersymmetric $SU(5)$ with the success of the minimal supersymmetric $SU(5)$ and minimal supersymmetric Flipped $SU(5)\times U(1)$ models. We show that a reasonable value for the universal soft supersymmetry-breaking gaugino mass, $45\GeV .114$. We define the supersymmetric standard model (SSM), the minimal supersymmetric extension of the standard model with gauge coupling unification and universal soft supersymmetry-breaking at the unification scale, as a baseline model for unified theories. We review the structure of the allowed parameter space of the SSM and suggest sparticle spectroscopy as the experimental means to determine the parameters of the SSM and search for departures from the baseline SSM.

hep-ph↗

arXiv1992

New Constraints on Neutralino Dark Matter in the Supersymmetric Standard Model

We investigate the prospects for neutralino dark matter within the Supersymmetric Standard Model (SSM) including the constraints from universal soft supersymmetry breaking and radiative breaking of the electroweak symmetry. The latter is enforced by using the one-loop Higgs effective potential which automatically gives the one-loop corrected Higgs boson masses. We perform an exhaustive search of the allowed five-dimensional parameter space and find that the neutralino relic abundance $Ω_χh^2_0$ depends most strongly on the ratio $ξ_0\equiv m_0/m_{1/2}$. For $ξ_0\gg1$ the relic abundance is almost always much too large, whereas for $ξ_0\ll1$ the opposite occurs. For $ξ_0\sim1$ there are wide ranges of the remaining parameters for which $Ω_χ\sim1$. We also determine that $m_{\tilde q}\gsim250\GeV$ and $m_{\tilde l}\gsim100\GeV$ are necessary in order to possibly achieve $Ω_χ\sim1$. These lower bounds are much weaker than the corresponding ones derived previously when radiative breaking was {\it not} enforced.

hep-ph↗

arXiv1992

Aspects of Radiative Electroweak Symmetry Breaking in Supergravity Models

We discuss several aspects of state-of-the-art calculations of radiative electroweak symmetry breaking in supergravity models. These models have a five-dimensional parameter space in contrast with the 21-dimensional one of the MSSM. We examine the Higgs one-loop effective potential $V_1=V_0+ΔV$, in particular how its renormalization-scale ($Q$) independence is affected by the approximations used to calculate $ΔV$ and by the presence of a Higgs-field-independent term which makes $V_1(0)\not=0$. We show that the latter must be subtracted out to achieve $Q$-independence. We also discuss our own approach to the exploration of the five-dimensional parameter space and the fine-tuning constraints within this approach. We apply our methods to the determination of the allowed region in parameter space of two models which we argue to be the prototypes for conventional (SSM) and string (SISM) unified models. To this end we impose the electroweak breaking constraint by minimizing the one-loop effective potential and study the shifts in $μ$ and $B$ relative to the values obtained using the tree-level potential. These shifts are most significant for small values of $μ$ and $B$, and induce corresponding shifts on the lightest $μ$- and/or $B$-dependent particle masses, \ie, those of the lightest stau, neutralino, chargino, and Higgs boson states. Finally, we discuss the predictions for the squark, slepton, and one-loop corrected Higgs boson masses.

hep-ph↗

arXiv1992

Constraints From Gauge Coupling Unification On The Scale Of Supersymmetry Breaking

We reanalyze precision LEP data and coupling constant unification in the minimal supersymmetric $SU(5)$ model including the evolution of the gaugino masses. We derive general bounds on the primordial gaugino supersymmetry-breaking mass-scale $m_{1/2}$ in terms of the various input parameters. The model cannot accommodate $m_{1/2}<1\TeV$ for values of $\as < 0.115$, even for extreme $1-σ$ values of the other inputs. We emphasize the sensitivity of this type of calculations to the various input parameters.

hep-ph↗